The US and the EU have separately urged the Cambodian government to undertake a thorough investigation of the shooting death of conservationist Chut Wutty.

Chut Wutty died along with a military policeman, In Ratana, in an exchange of gunfire in remote Koh Kong province that has left many unanswered questions.

The government has established an investigative committee, and two men have been detained for questioning in the April 26 shooting. However, neither of them has been charged with a crime.

The US Embassy on Thursday urged the government “to undertake a thorough, transparent, and credible investigation into this matter.”

“Furthermore, the United States encourages authorities to prosecute anyone found responsible in a similarly transparent and credible manner,” the embassy said. “The United States remains concerned about the use of force to curb the actions of individuals seeking to peacefully shed light on important issues like illegal logging.”

The EU said in its own statement it was concerned with ongoing violence toward environmental activists.

The UN office of human rights said the shooting was the fifth this year involving live ammunition use against civilians and rights workers.

“Despite the current lack of clarity about what exactly happened, we are very concerned that the killing of Mr. Wutty marks the latest and most lethal in a series of gun attacks on human rights defenders in Cambodia,” Rupert Colville, a spokesman for the Office of the UN High Commissioner for Human Rights, said. “We also urge the Government to take concrete and immediate measures to ensure the safety of all witnesses and investigators as well the families of the deceased men.”